Fuel pump diaphragm assembly



n 24, 1 5 E. A. JQHNSON ETAL 2,840,003

FUEL PUMP DIAPHRAGM ASSEMBLY I Filed Sept. 16, 1954 INVENTOR. ELDON A.JOHNSON JACK .WHITE ATTORNEY 2,840,003 FUEL PUMP DIAPHRAGM ASSEMBLYEldon A. Johnson, St. Louis, and Jack M. White, Normandy, Mo.,assignors, by mesne assignments, to ACF Industries, Incorporated, NewYork, N. Y., a corporation of New Jersey Application September 16, 1954,Serial No. 456,360

3 Claims. 01. 103-150 This invention relates to engine driven fuelpumpsof the diaphragm type and, more specifically, to means for increasingthe durability and volumetric efliciency of this type of pump.

In present pulsating fuel pump design, a circular, flexible diaphragm isclamped at its periphery between the circular flanges of the rockerarmcasing and the valve casing of the pump. The diaphragm is flexed toproduce the pumping action by a stem connected to, the diaphragm andreciprocated from a cam driven rocker arm. This connection with the stemis secured centrally to the diaphram by a pair of backing plates lockedto the free end of the stem in clamping relation to the diaphragm.Duringpump assembly, it is usual to provide sufficient slack in thediaphragm outside of the backing plates to accommodate the reciprocatingaction of the backing plates during their movement from one extreme endof the stroke to the other. Although the diaphragm is of flexiblematerial, it cannot be repeatedly stretched or crimped without fracture.Because there will always be slack in the diaphragm in the midstrokeposition of the hacking plates,. a circumferential wrinkle or' loop isformed between the backing plates and the pump chamber. On the suctionstroke, this wrinkle will form a loop on one side of the backing plates,but, on the pressure stroke, this wrinklewill form a loop in theoppositedirection. This inherent back and forth switching of the flexing loop ofthe diaphragm substantially reduces the life of the diaphragm as well asthe capacity, of the pump,

since adequate space must be provided between thesults in a larger loopstructure, in orderto. avoid fric tional scraping together of the wallsof the loop cessive crimping of the loop. I

This space within the wrinkle contributes to the occurrence of vaporlock. Space must be minimized in order to attain the maximum possiblevolumetric efficiency to handle modern fuels which contain highlyvolatile ends. Experiments 7 with larger backing plates to obtain thisobjective have not been successful, since such plates cause kinking andfrictional interference in the flexing portions of the diaphragm.Moreover, when the backing plates exceed a certain size in relation tothe pump, the diaphragm acts as an over-center type of spring on eachstroke. This is not too important on the suction stroke, because thepump is being actuated by the engine driven eccentric. The dischargestroke of the pump is spring powered, however, and the opposing springaction of the diaphragm can prevent the pump from developing itsdesigned discharge pressure at low speeds and stall the pump at highengine speeds.

This invention has as its object to increase the volumetand exricefiiciency in this type of pump without the disadvan' the wrinkle formedin the diaphragm on each opposite stroke. This arrangement of thebacking plates requires that the wrinkle in the diaphragm will form aloop in one direction only in such a manner that its displacement isalso utilized toreduce clearance and improve the volumetric etficiency.

The accompanying drawings illustrate one manner in which the inventionmay be carried out.

In the drawings, Fig. 1 is a side elevation, partly in section, of apump constructed according to the present invention.

Fig. 2 is a detail of the diaphragm and backing plate assembly for thatpump shown in section. V Fig, 3 is a fragmentary view, partly insection, of a, pump according to this invention showing the position ofthe parts at the discharge end of the stroke.

Fig. 4 is a similar view to Fig. '3 showing the relation of the parts atthe extreme opposite end of the stroke.

'Fig. 5 is a view similar to Figs. 3 and 4 showing the position of theparts at midstroke.

Fig. 6 is a view similar to Fig. 5 of a modified form of the invention.

The pump shown in Fig. 1 of the drawings is the same type as that shownin a patent of Irven E. Cofiey, No. 2,625,114 andreference may be madeto this patent for the detailed construction not shown in the presentapplication. Y

j The pump shown in Fig. 1 has a rocker arm casingl with a flange 2having bolt holes (not shown) to secure the pump to the engine of themotor vehicle. Within ,the rocker casing '1 is an arm 3 which isnormally discharge stroke. Theintake stroke is etfected by the. actionof the rocker arm 3 against theresistance of spring,

10. Stem 9 has a shoulder 11 and a reduced extension 12 extending beyondthe shoulder, upon which the backing plates and diaphragm are mounted.Diaphragm 13 is held between an outer or upper backing plate 14 outsidethe pump chamber and, alower or inner backing plate 15 on the inside ofthe pump chamber. These plates are mounted on reduced extension 12 by apair of washers 16 and'17. The diaphragm 13 includes a central portionclamped between the backing plates 14 and 15, and vouter annular portionof bight form which proscribed in detail, in the application of James L.Edelen,

a in position on the stem 9, and has a similarly turned,

jectstowar'ds the pump chamber, and a peripheral portion whichis clampedbetween the flanges 25 and 26 of the, housing. Washer 17 looks with thereversely tapered end of the reduced extension 12, all as illustratedand de- Serial Number 429,343, filed May 12, 1954, for Shaft End;Mounting for Sealing and Loop Forming a Pump Diaphragm. Outer backingplate 14 may be provided with an intermediate rib 19 forming aseat forspring 10.

According, to this invention, outer backing plate 14 is larger thaninner'backing plate 15, and is provided adjacentits periphery with adownturned lip 20 which erminates in a reversely rolled edge or curvedlip 21.

Inner backing plate 15 is substantially flat when securedcomplementarylip 22 disposed in parallel relation and radially inwardlyof or underlying the overhanging lip 20 ,of .outer backing plate 14. h

As can be seen from Fig. 2, the complementary lips on the backing platesgrip and stress the diaphragm 13 to effect a distinct frusto-conicaldeformation or bight 30 in the diaphragm from a normally flat condition.This distortion is clearly illustrated in Fig. 2. Referring again toFig. 1, the periphery of the diaphragm 13 is clamped between thecircular peripheral flange 25 of the rocker arm casing 1 and thecorresponding flange 26 of the il'a'lve'chaiiiber casing 27'by a seriesof cap screws 28. Sufficient. slack is provided in the flexingportion'or bight 300i the diaphragm between the backing plates and thecasingsoas tapermit the full stroke of the pump without stretching thispart ofthe diaphr'agmi.

A dome jformin'g cover31' with an outlet is secured to theva1ve"body 27infahy suitable mannei Iui'nin'g jnow to'FigsI 3fto5, Fig. 3'illustrates the operation of thediaphr'agrn within theipump chamber 35at the extreme, end of the discharge stroke of the chamber 35 to providefull volumetricefiiciency. This is important since it enables the pumpto better handle gases to prevent vapor lock. s

Fig.1 4 "illustrates the pump elements atlthe extreme end oft he'suction stroke. In this position, the bight 30 in the diaphragm 13 is inthe same relation tothe backing plates as in Fig; 3, due, tothe'st'resses produced on the diaphragm by the backing plates.

Fig. 5 illustrates the, position'of the pumping elements at midstroke,and here again the position of the bight 30 in the diaphragm 13 is shownmaintained in the same looped relation to the backing plates as in theprevious views. 7 'It .will be noted that the action of the diaphragmphragm, and permits use of larger backing washers with:

out undue kinking" or scraping "of the diaphragm during operation. V

In Fig. 6 is shown a modification of the invention wherein lip 21 of theouter backing plate has a cylindrical outwardextension 21A disposed.closely adjacent to the walls of the pumping chamber. This flange willfurther assist in precluding reversal in the position of the bight 30,should there be anytendency for this effect.

structure has beenfshown which will fulfill all the objects of thepresent invention as defined by the appended claims, but itiscontemplated that other embodiments of the same invention will occurto those skilled i'n'the art. l

We claim; I M g 1. A fuel pump comprising a casing forming a pumpingchamber, said pumping chamber having its end wall portion provided withinletand outlet openings, a diaphragm forming a pumping element and onewall of said chamber, said diaphragm havingitsfouter peripheral portionsecured to the casing, said diaphragm being provided with aninwardlyprojecting bight at its outer portion, backing plates disposed upon theinner and outer sides of a central portion of the diaphragm, a centrallypositioned'operating stem connected thereto, spring means on the stemnormally urging said diaphragm into said pumping chamber, the peripheraledge of said inner plate being spaced a sutficient distance from thewall of said portion normally projecting into the concave portion of'said bight and engaging the adjacent face of the diaphragm defining thebight for retaining said bight against substantial deflection regardlessof pressure in said pumping chamber.

2. A fuel pump comprising a casing forming a pumping chamber, saidpumping chamber having its end wall portion provided with inlet andoutlet openings, a diaphragm forming a pumping element and One wall ofsaid chamber, said diaphragm having its outer peripheral portion securedto the casing, said diaphragm being provided with an'i'nwardlyprojecting bight at its outer portion,"

nating in a reversely curved lip, and said peripheral por-' tionnormally projecting into the concave portion of said' bight and engagingthe adjacent face of the diaphragm defining the bight for retaining saidbight against substantialdeflection' regardless of pressure in saidpumping chamber." V i 3. *A fuel pump comprising a casing forming apumping chamber, said pumping chamber having its end wallportiomprovided with inlet and outlet openings, a dia-' phragrn forminga pumping element and one wall of said chamber; said diaphragm havingits outer peripheral portion secured to the casing, said diaphragm beingprovided with an inwardly projecting bight at its outerportion, backingplates disposed upon the inner and outer sides of acentral portion ofthe diaphragm, a centrally positioned operating stem'connected thereto,spring means on the stemnormally urging said diaphragm into said pumpingchamber, the peripheral edge of said inner plate being spacedasuflicient distance from the wall of said chamber.

to provide an annular area between said wall and said plate topermitsaid bight in said diaphragm to project therebetween in the direction ofthe pumping chamber,

said peripheral portion of the inner backing plate extending alongjtheadjacent inner face of the bight to guide and retain the sameagainstdefiection inwardly, and the peripheral portion -'of the outerbacking plate being spaced References Cited in the file of this patent fV "U ITED STATES PATENTS Pounds May 4, 1875 1,466,242 Neal Aug. 28, 19231,811,557 Ove a June 23, 1931 2,080,391 i Rockwell May 11, 19372,169,862 Whitted Aug. 15, 1939 2,185,784 Corydon et al. Ian. 2, 19402,464,196 Van Ranst Mar. 8,' 1949 2,623,726 Suska Dec. 30, 1952 FOREIGNPATENTS 102,368 Great Britain Nov. 30, 1916 405,686 Great Britain Feb.12, 1934 616,053 France Oct. 25, 1926

